A MEMS sensor such as a gyroscope or accelerometer formed in a semiconductor process requires forming a movable structure with a certain mass. A relatively thick layer is provided and patterned to form a proof mass that is coupled to the remaining structures by flexible supports, which allow the mass to move in certain directions. Anchor structures are formed and some of the flexible supports are coupled to the anchor structures. The mass and the anchors, or sensing electrodes coupled to them, have portions that form plates of a variable capacitance. When the mass is displaced by motion, some of the capacitances increase and some decrease, depending on the direction of motion. By sensing the changes in the capacitances, an electrical signal that corresponds to the motion can be output. The gap spacing between the capacitive plates formed on or coupled to the mass and those of the anchors determines in part the characteristics of the capacitance. In prior approaches, this gap spacing is limited by the characteristics of an etch process used to form the structure, limiting the ability to form MEMS structures with the gap spacing needed to provide the required sensitivity in the MEMS device.
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The figures are drawn to clearly illustrate the relevant aspects of the embodiments and are not necessarily drawn to scale.